The present invention concerns a logic system for preprocessing alarms, applicable inter alia to centrally controlled digital switching telephone networks.
In large systems controlled centrally by a computer, alarms are transmitted over a route other than those taken by data and commands, since in the event of a major fault in one part of the system (power supply failure, for example), functional links are not able to transmit data on the nature and location of the fault.
Also, as alarms may be generated by a large number of decentralised equipments, the use of functional links to carry these would rapidly lead to congestion.
Although the computer(s) of the exchange can access all units without reference to the hierarchy of functional links, this calls for a significant amount of analysis and programming work to determine the nature of alarms and their degree of priority. This reduces the speed at which it is possible to intervene to prevent fault conditions propagating, resulting in a proportional decrease in the capacity for processing functional data.